1. Field of the Invention
The present invention relates to methods, systems and apparatus for monitoring and adjusting indoor air quality. More specifically, the present invention relates to methods and apparatus for monitoring and adjusting indoor air quality by sensing and removing indoor air contaminants.
2. Present State of the Art
Heating, Ventilation, and Air Conditioning (HVAC) systems can be designed to control the temperature and humidity of indoor air by combining fresh outside air with recirculated inside air. This process is tempered by air heating and cooling costs. The quality of the indoor air is usually determined by the temperature and humidity of the air. Typically, the ratio of outside air to inside air is fixed and adjustments to the ratio are usually made manually when there is concern about the quality of the indoor air.
HVAC systems relying on the manual adjustment of the ratio between outside air and recirculated indoor air are not economically optimized and have the potential to subject personnel to unknown hazardous contaminants. For example, when the indoor air quality is very good, the HVAC system draws and conditions more outside air than is needed, which increases cost because the excess outside air has to be heated and conditioned. When air quality is poor, not enough outside air is drawn into the system resulting in health risks to personnel, which in turn leads to increased costs due to overexposed personnel, loss of productivity, and increased facility maintenance.
More advanced HVAC system have the added ability to sense particulates, Volatile Organic Compounds (VOC), and carbon dioxide but do not address hazards from exposure to a wide range of contaminants. The ability to sense particulates and carbon dioxide has improved the efficiency of HVAC systems, but not all problems have been solved. In fact, numerous instances of workplace problems related to the quality of indoor air have been recorded. The recirculation of indoor air can permit odors and toxic gases to concentrate over time and ultimately leads to unhealthy indoor air. The sources of these contaminants can include: facility infrastructure such as carpet, paints, and furniture; electrical equipment such as photocopiers, video monitors and ovens; cleaning equipment and supplies; mechanical equipment fuels, lubricants and combustion byproducts; the use of tobacco and perfumes by personnel; and natural microbes such as those found in drains, vents and crawl spaces.
Most of the recorded incidents related to poor indoor air equality were attributed to air contaminated with volatile organic compounds (VOC) from paints, adhesives and polishes along with nitrogen containing compounds such as nitric acid, nitrogen dioxide, and ammonia. These incidents occur because most HVAC systems are maintained by manually altering the indoor airflow and recycling rates based on personal observations and experience with odors, hazes, and weather conditions. However, none of these systems provide a mechanism to recognize when non-visible or non-odorous contaminants are present. If the control of any of these rates is controlled automatically, it is typically based on some combination of humidity, temperature, smoke and carbon dioxide. Routine monitoring and control of regulated contaminants specified in the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standard 62xe2x80x94and its revisions is rare. Further, these systems do not take into account the status or quality of the outside air being introduced into the system.
The Clean Air Act of 1970 required the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for the six most significant air pollutants in the outdoor environment: sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, lead, and particulate matter with a diameter less than or equal to 10 micrometers. Of these pollutants, sulfur dioxide, nitrogen dioxide, carbon monoxide and ozone are colorless at very low concentrations and significantly and adversely affect human health. Current HVAC systems usually presume the outside air to be free of contaminants and do not monitor or make adjustments for these or other contaminants.
In addition to the contaminants and pollutants found in outside air, many other contaminants can be the cause of harmful indoor air. Currently, general indoor air quality is not regulated, but many agencies have proposed standards which may serve as guidelines. Standards have been proposed by the U.S. Department of Labor""s Occupational Safety and Health Administration (OSHA), the World Health Organization (WHO), and ASHRAE. The pollutants and contaminants these standards propose regulating include: carbon dioxide, carbon monoxide, formaldehyde, nitrogen dioxide, ozone, radon and progeny, sulfur dioxide, and a number of VOCs. In addition to these contaminants, many other chemicals are regulated by OSHA in work environments to control long and short-term exposures.
As noted above, HVAC manufacturers typically purchase sensors to monitor temperature, smoke, humidity and carbon dioxide. Providing additional sensors to monitor all potentially harmful contaminants is rare and expensive because of the cost of providing sensors for each contaminant. The addition of charcoal filters, water scrubbers, and reductant/oxidant scrubbers as a means of ensuring good indoor air is also impractical because they have a limited capacity that is exhausted rapidly during continuous operation. In other words, it is impractical to provide a sensor or filter for each contaminant and pollutant. There remains a need, however, to sense poor indoor air quality and make adjustments to the indoor air such that human health is preserved and economic costs are lowered.
The present invention has been developed in response to the present state of the art, and in particular, in response to these and other problems and needs that have not been fully or completely solved by currently available HVAC systems for monitoring and adjusting the quality of indoor air. Thus, it is an overall object of the present invention to provide a method, system and apparatus for reliably monitoring and adjusting the quality of indoor air.
It is therefore an object of one embodiment of the present invention to monitor abnormal conditions indicative of unhealthy air.
It is another object of one embodiment of the present invention to monitor and adjust the quality of indoor air.
It is a further object of one embodiment of the present invention to minimize heating and cooling costs.
It is an additional object of one embodiment of the present invention to protect humans from over exposure to hazardous air pollutants.
It is another object of one embodiment of the present invention to identify contaminants and pollutants in the indoor air.
It is a further object of one embodiment of the present invention to infer the identity of contaminants and pollutants in the indoor air.
Yet another object of one embodiment of the present invention is to determine when alternative air supplies or mitigation processes should be used to provide healthy indoor air.
In summary, the foregoing and other objects are achieved by providing a method and apparatus for monitoring and adjusting the quality of indoor air. In one embodiment of the present invention a sensor array is provided which is capable of sensing a variety of contaminants. Each contaminant or mixture of contaminants may cause the individual sensors in the sensor array to produce a particular sensor signature or output. Further, each contaminant also causes the sensors to produce an array signature. Both the sensor signatures and the array signatures can be indicative of particular contaminants.
In this manner, personnel can be protected from over exposure to toxic substances and the costs associated with heating, cooling, and humidifying the air can be minimized. Another embodiment also monitors the outside air to ensure that harmful contaminants are not introduced from the outside air.
The signatures are sent to a processing unit which compares the signatures to a database or library of known signatures. Based on this comparison, the contaminant is identified or the identity of the contaminant is inferred. Once identified, the system evaluates the level of hazard presented by the contaminant and takes corrective action to remove the contaminant from the indoor air. An exemplary corrective action is to adjust the ratio of outside air mixed with recycled inside air to reduce the concentration of the contaminant to an acceptable level.
The combination of sensors and the database of signatures enables the present invention to monitor a number of contaminants beyond the contaminants that the sensors can monitor individually. Effectively, the sensor array can be represented by an n-dimensional space. The signatures of various contaminants are mapped within this n-dimensional space. The signatures of known contaminants are stored in a database and the signatures of sensed contaminants are compared to that database. The n-dimensions permit the identity of unknown contaminants to be inferred if the signature of the unknown contaminant is spatially near the signature of a known contaminant.
By adding more dimensions to the sensor array, which is done by adding additional senors, the accuracy of identifying the contaminant is increased. In an n-dimensional database, the interpolation between database points, which represent contaminants, is easily done and quite accurate because the points are not far apart spatially. Also, the n-dimensions of the database allows for more separation between the clusters of points, which results in better accuracy and the possibility of storing data on more contaminants. The present invention is also capable of learning to identify new contaminants and the database of known contaminants and pollutants can continually be updated and increased.
Another embodiment of the present invention is that the system can decide which sources of air to use to assure healthy indoor air. The source could be another outside air inlet vent, mitigated recirculated indoor air, or a reservoir of purified air. If the source of air is unacceptable, the contaminants are first removed or reduced before the air is introduced into the system. This is accomplished by sensing the contaminants present in the air and then passing the air through a series of modules or filters which strip the contaminants from the air before the air is mixed and introduced into the system. In a preferred embodiment, the modules or filters are active only when contaminants are present in the outside air or the recirculated air.
One embodiment of the sensors array is capable of sensing a wide variety of contaminants including but not limited to carbon dioxide, carbon monoxide, sulfur dioxide, hydrogen sulfide, nitrogen oxides and a variety of volatile organics. In addition to these contaminants, the humidity, pressure and temperature of the air also monitored. In some cases, other specific sensors maybe added when the specific location has a historical record of other ambient contaminants.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.